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Re: New discussion: ppc64 installer -- ext2 /boot partition to keep sabot happy.

On 10/01/2017 12:47 PM, Frank Scheiner wrote:
> I recently stumbled upon [1] which mentions an "8M" limit (either 8 MB or
> 8 MiB) for the PReP partition which holds the stage1 binary - most likely yaboot or
> grub - for IBM POWER machines.
> [1]: https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/W51a7ffcf4dfd_4b40_9d82_446ebc23c550/page/PowerLinux%20Boot%20howto
> This is also reflected in the current partman recipes for "powerpc-chrp_ibm" and "powerpc-prep" (and respective ppc64 targets) on [2]:
> Example:
> root/recipes-powerpc-chrp_ibm/atomic
> ```
> [...]
> 8 1 1 prep
>     $primary{ }
>     $bootable{ }
>     method{ prep } .
> [...]
> ```

Yes, I know.

> So maybe 8 MB/MiB as maximum size for the PReP partition could also be a good candidate
> for the size of the HFS partition on Apple powerpc and ppc64 machines.

Well, I assume the PREP partition works differently than Apple's HFS partition.

> As mentioned before, I don't know how to mount this PReP partition on my POWER5
> machine.

You don't mount it and debian-installer doesn't either. GRUB takes care of the
PREP partition and directly installs into it using the "grub-install" command.

> I assumed there is a VFAT FS on this partition, but mounting it as VFAT
> doesn't succeed. So maybe there's no FS at all on this partition but just
> a stage1 binary. Maybe it's dd'ed directly to this partition - if someone could shed
> some light on this, I'd be grateful. :-)

I don't really think we need to dig into what's inside PREP. We only need to
figure out why partman in debian-installer isn't flagging the first partition
as "PREP".

> One other thought:
> It could also be that the size of the partition is not an issue for the firmware,
> but the size of the stage1 binary could be. The original 800 KB limit on Power
> Macs could be also to make sure, that the stage1 binary cannot be bigger than
> 800 KiB, which was the same size as a Mac 3.5" floppy disk according to Rogério
> Brito on [3].

I don't think this is of our concern either. GRUB knows the limitations and
takes care of them.


 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

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